Controllable Preparation And Energy Storage Mechanism Of Vanadium-based Aqueous Zinc-ion Battery Cathode Materials

Electrochemical energy storage equipments are playing a vital role in renewable energy infrastructure and effective utilization.Because of the advantage of low price,safety,non-toxicity,environmental friendliness,and easy handling,aqueous zinc ion batteries（ZIBs）have become one of the most promising energy storage devices in the large-scale energy storage system.This article focuses on the development and application of high performance vanadium-based zinc-ion battery cathode materials,following the ideas that the design,synthesis,modification,characterization,and energy mechanism.Herein,we developed Zn//V₂O₅ hybrid-ion batteries in Zn（CF₃SO₃）₂-Li TFSI mixed ion electrolyte with high voltage and long cycling performance.We developed the porous V₂O₅ microspheres cathode material with a spray-drying method.Advanced in-situ XRD and ex-situ XPS were used to study the structural evolution of Zn²⁺intercalation/de-intercalation into/from porous V₂O₅microspheres.Moreover,we first developed Na₂V₆O₁₆·1.63H₂O nanowire cathode with a simple hydrothermal method.Advanced ex-situ XRD and XPS characterization and electrochemical measurements were performed to confirm that the interlayer H₂O can provide an ultrastable skeleton structure for highly reversible Zn²⁺intercalation and de-intercalation.We developed Na₃V₂（PO₄）₃@reduced graphene oxide microspheres（NVP@r GO）by the spray-drying method.We find that NASICON structured Na₃V₂（PO₄）₃ manifests simultaneous Zn²⁺/Na⁺intercalation/de-intercalation in a single component electrolyte（2.0 M Zn（CF₃SO₃）₂）.Based on above research contents,a series of meaningful research and understanding were obtained as follows:（1）We constructed the porous V₂O₅microplates with hydrothermal assisted high-temperature sintering strategy.The specific capacity,cyclic stability,rate performance,and energy storage mechanism of the porous V₂O₅ in Zn（CF₃SO₃）₂ and Zn（CF₃SO₃）₂-Li TFSI electrolytes were investigated by charge/discharge profiles and in-situ XRD.The porous V₂O₅ cathode material in Zn（CF₃SO₃）₂-Li TFSI delivers a high discharge capacity of 215 m Ah g^-1 at 50 m A g^-1.After 160 cycles,95%(204m Ah g^-1)of the highest capacity can be maintained.These electrochemical performance are superior to the porous V₂O₅in Zn（CF₃SO₃）₂.（2）We developed porous V₂O₅ microspheres via a spray-drying assisted high-temperature sintering method.The morphology,structure,pore size distribution and V valence state of porous V₂O₅ microspheres were systematically characterized.The electrochemical characterization and in-situ XRD demonstrated that the porous V₂O₅ microspheres exhibited higher capacity,more excellent long cycling performance and better rate performance than VO_x/C-350 and VO_y/C-500.The porous V₂O₅ microspheres deliver a capacity of 219 m Ah g^-1 at 100 m A g^-1,increasing to 401 m Ah g^-1 at the first 15^th cycles,with an average voltage of 0.713 V and the energy density can reach to 286 Wh kg^-1.（3）We developed a Na₂V₆O₁₆·1.63H₂O nanowire（H-NVO）with interlayer water through a simple hydrothermal method.The morphology,structure,and V valence state of H-NVO were systematically characterized.Based on electrochemical characterizations,ex-situ XRD/XPS,and the results of single-nanowire zinc-ion battery,we disclosed that the existence of structural water would contribute a great improvement to the cycling stability of ZIBs,making the electrochemical performances of H-NVO outperform the Na V₃O₈ nanowire without interlayer water.The H-NVO nanowire can maintain 90%of the initial capacity after 6000 cycles at a high current density of 5000 m A g^-1.The application of single-nanowire ZIB would push the fundamental and practical research of nanowire electrode materials for energy storage applications.（4）We designed and constructed NVP@r GO microspheres via a spray-drying assisted high-temperature sintering method.After systematically characterized the morphology,structure,and V valence state,we find that the NVP@r GO microspheres deliver an excellent electrochemical performance.The NVP@r GO delivers an initial capacity of 114 m Ah g^-1 with an average voltage of 1.27 V,and the energy density can reach to 145 Wh kg^-1.On the basis of ex-situ XRD and XPS,we disclosed that the NVP@r GO microspheres manifest simultaneous Zn²⁺/Na⁺intercalation/de-intercalation in a single component electrolyte（2 M Zn（CF₃SO₃）₂）.This work sheds light on the development of secondary batteries with hybrid ion intercalation/deintercalation behaviors using a single component electrolyte.